Optical circulator array

ABSTRACT

Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for optical communications. In one aspect, an optical circulator array includes a plurality of stacked three port circulators each having a respective first port of a first port array, a respective second port of a second port array, and a respective third port of a third port array, wherein each of the plurality of staked three port circulators share optical components including: a first Wollaston prism coupled to the first port array, a first lens, a first half wave plate, a polarization dependent beam path separator, a second half wave plate, a second lens, a propagation direction dependent polarization rotation assembly, a second Wollaston prism coupled to the second port array, and a third Wollaston prism coupled to the third port array.

BACKGROUND

This specification relates to optical communications.

Conventional optical circulators are employed in systems transmittingoptical signals in order to transmit optical signals in a particulardirection. For example, in a three port optical circulator, an opticalsignal input at the first port will be transmitted to the second port.An optical signal input at the second port will be transmitted to thethird port. However, optical signals typically will not be transmittedin the reverse direction. For example, an optical signal input at thesecond port will not be transmitted to the first port.

SUMMARY

In general, one innovative aspect of the subject matter described inthis specification can be embodied in optical circulator arrays thatinclude a plurality of stacked three port circulators each having arespective first port of a first port array, a respective second port ofa second port array, and a respective third port of a third port array,wherein each of the plurality of staked three port circulators shareoptical components including: a first Wollaston prism coupled to thefirst port array, a first lens, a first half wave plate, a polarizationdependent beam path separator, a second half wave plate, a second lens,a propagation direction dependent polarization rotation assembly, asecond Wollaston prism coupled to the second port array, and a thirdWollaston prism coupled to the third port array.

The foregoing and other embodiments can each optionally include one ormore of the following features, alone or in combination. In particular,one embodiment includes all the following features in combination. Thepropagation direction dependent polarization rotation assembly includesa Faraday rotator and a half wave plate. Each port array includes one ormore thermal expansion core (TEC) fibers. The polarization dependentbeam path separator includes a birefringence wedge pair. Thebirefringence wedge pair includes: a first wedge optically coupled to afirst side of the birefringence wedge pair; and a second wedge opticallycoupled to a second side of the birefringence wedge pair, wherein thefirst wedge and the second wedge correct parallelization of light beamspassing through the optical circulator array. The polarization dependentbeam path separator includes an optical beam separator with polarizationdependent coating. The TEC fibers, first lens, second lens, andpolarization dependent beam path separator are positioned in a doubletelemetric configuration layout. The polarization dependent beam pathseparator provides beam path routing from the first port to the secondport and from the second port to the third port based on a polarizationorientation of incident light beams. The polarization dependent beampath separator is optically coupled between the first lens and thesecond lens. The propagation direction dependent polarization rotationassembly is optically coupled between the second Wollaston prism and thesecond lens.

The optical circulator array further includes a second propagationdirection dependent polarization rotation assembly coupled to the firstport; and a third propagation direction dependent polarization rotationassembly coupled to the third port, wherein the second propagationdirection dependent polarization rotation assembly is optically coupledbetween the first Wollaston prism and the first lens, and the thirdpropagation direction dependent polarization rotation assembly isoptically coupled between the third Wollaston prism and the first lens.The second propagation direction dependent polarization rotationassembly provides isolation to reduce light leakage along a path fromthe second port to the first port. The third propagation directiondependent polarization rotation assembly provides isolation to reducelight leakage along a path from the third port to the second port. Lightbeams input at the first port are randomly polarized and wherein thefirst Wollaston prism and the first half wave plate provide polarizationconditioning.

In general, one innovative aspect of the subject matter described inthis specification can be embodied in optical circulator arrays thatinclude a plurality of stacked three port circulators each having arespective first port of a first port array, a respective second port ofa second port array, and a respective third port of a third port array,wherein each of the plurality of staked three port circulators shareoptical components including: a first micro lens array optically coupledto the first port array and the third port array, a first walk offcrystal, a first half wave plate, a first faraday rotator, a firstbirefringence wedge pair, a second birefringence wedge pair, a secondFaraday rotator, a second half wave plate, a second birefringence walkoff crystal, and a second micro lens array optically coupled to thesecond port array.

Particular embodiments of the subject matter described in thisspecification can be implemented so as to realize one or more of thefollowing advantages. An optical circulator array allows multiple threeport circulators to be stacked so that they each use a common set ofoptical components. The array of circulators can be alignedsubstantially concurrently.

The details of one or more embodiments of the subject matter describedin this specification are set forth in the accompanying drawings and thedescription below. Other features, aspects, and advantages of thesubject matter will become apparent from the description, the drawings,and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a diagram of an example optical circulator array on a portbeams routing Y-Z plane.

FIG. 1B is a diagram of an example single optical circulator of theoptical circulator array of FIG. 1A on a polarization conditioning X-Zplane.

FIG. 1C is a diagram of the example optical circulator array of FIG. 1Aon an array stacking and polarization conditioning X-Z plane.

FIG. 2A is a diagram of an example optical circulator array on a portbeams routing Y-Z plane.

FIG. 2B is a diagram of an example single optical circulator of theoptical circulator array of FIG. 2A on a polarization conditioning X-Zplane.

FIG. 2C is a diagram of the example optical circulator array of FIG. 2Aon an array stacking and polarization conditioning X-Z plane.

FIG. 3A is a diagram of an example circulator array on a port beamrouting and polarization conditioning Y-Z plane.

FIG. 3B is a diagram of the example circulator array of FIG. 3A on anarray stacking X-Z plane.

Like reference numbers and designations in the various drawings indicatelike elements.

DETAILED DESCRIPTION

FIGS. 1A-C illustrate an example optical circulator array 100. FIG. 1Ais a diagram of the example optical circulator array 100 on a port beamsrouting Y-Z plane. FIG. 1B is a diagram of an example single opticalcirculator of the optical circulator array 100 of FIG. 1A on apolarization conditioning X-Z plane. FIG. 1C is a diagram of the exampleoptical circulator array 100 of FIG. 1A on an array stacking andpolarization conditioning X-Z plane showing light paths for multiplecirculators of the optical circulator array 100.

The optical circulator array 100 includes a first port array 101, asecond port array 113, and a third port array 117. The opticalcirculator array 100 is configured such that an input beam from anoptical fiber at the first port array 101 is routed to an output opticalfiber at the second port array 113 and that an input beam from anoptical fiber at the second port array 113 is routed to an output fiberat the third port array 117. The optical circulator array 100 providesan array of multiple three port optical circulators stacked on the X-Zplane. Each optical circulator of the array shares the optical ports andoptical components. The optical circulators of the array can be alignedat the same time.

FIG. 1A shows beam paths for an optical input from the first port array101 to output at the second port array 113 and an optical input from thesecond port array 113 to output at the third port array 117.

Each of the first port array 101, second port array 113 and third portarray 117 can include or be coupled to one or more thermal expansioncore (TEC) fiber that allows multiple optical signals to be input andoutput from the respective port arrays of the optical circulator array100. A TEC fiber has an enlarged mode field diameter obtained throughheating relative to a typical single mode optical fiber.

With reference to FIG. 1A, a light beam input at the first port array101 through a corresponding TEC fiber has a random polarization. Theinput beam passes through a first Wollaston prism 102. The firstWollaston prism 102 includes a pair of wedge prisms. The optic axes ofthe wedge prisms are perpendicular to each other such that the lightbeam exiting the Wollaston prism 102 diverges based on polarizationdirection such that two orthogonally polarized light beams result. Afterthe TEC fiber the Gaussian beam divergence angle is reduced that allowstwo orthogonally polarized light beams to be clearly separated angularlyby Wollaston prism 102. A C-axis of the first wedge prism of theWollaston prism 102 is parallel to the X-Z plane and the C-axis of thesecond wedge prism of the Wollaston prism 102 is perpendicular to theX-Z plane.

The light beams exiting the Wollaston prism 102 then pass through afirst propagation direction dependent polarization rotation assembly.The first propagation direction dependent polarization rotation assemblyincludes a first 45 degree Faraday rotator 103 and a first 22.5 degreecut half wave plate 104. In the propagation direction from the firstport array 101 to the second port array 113, the first propagationdirection dependent polarization rotation assembly provides zero degreesof polarization rotation. The light beams then pass through a first lens105, which collimates the light beams so that they are substantiallyparallel.

As shown in FIG. 1B illustrating beam paths for a single opticalcirculator along the X-Z plane, one of the two orthogonally polarizedlight beams that is polarized parallel to the X-Z plane passes through a45 degree cut half wave plate 106 such that its polarization is rotatedby 90 degrees to the direction that is perpendicular to the X-Z plane.The light beam exiting the 45 degree cut half wave plate 106 is directedto a Y-Z plane birefringence wedge pair or Wollaston prism 107.

The other orthogonally polarized light beam is polarized perpendicularto the X-Z plane is directly passed to the Y-Z plane birefringence wedgepair 107, which may be another Wollaston prism. Consequently, the twolight beams have the same polarization direction upon entering the Y-Zplane birefringence wedge pair or Wollaston prism 107.

The Y-Z plane birefringence wedge pair or Wollaston prism 107 isconfigured such that it passes the light beams having the samepolarization direction that is perpendicular to the X-Z plane from abeam path corresponding to the first port array 101 to a beam pathtoward the second port array 113. The light beam that corresponds to thebream that passed directly from the first lens 105 to the Y-Z planebirefringence wedge pair or Wollaston prism 107 is then passed through a45 degree cut half wave plate 108 resulting in a polarization rotationof 90 degrees to the direction that is parallel to the X-Z plane. Thelight beam exiting the 45 degree cut half wave plate 108 is directed toa second lens 109.

The other light beam, which passed through the 45 degree cut half waveplate 106, is directly coupled to the second lens 109 without passingthrough the 45 degree cut half wave plate 108. Therefore, the light beamremains polarized in the direction perpendicular to the X-Z plane as itis coupled to the second lens 109.

The Y-Z plane birefringence wedge pair 107 includes two crystal wedgeshaving orthogonal axes to each other. The C-axis of the first wedge ofthe Y-Z plane birefringence wedge pair 107 is perpendicular to the Y-Zplane and the C-axis of the second wedge of the Y-Z plane birefringencewedge pair 107 is parallel to the Y-Z plane.

After the light beams pass through the second lens 109, the light beamsare coupled to a second propagation direction dependent polarizationrotation assembly. The second propagation direction dependentpolarization rotation assembly includes a second 45 degree Faradayrotator 111 and a second 22.5 degree cut half wave plate 110. In thepropagation direction from the first port array 101 to the second portarray 113, the second propagation direction dependent polarizationrotation assembly provides zero degrees of polarization rotation.

After passing through the second propagation direction dependentpolarization rotation assembly, the light beams are coupled to a secondWollaston prism 112. The second Wollaston prism 112 includes a pair ofwedge prisms. The C-axis of the first wedge of the second Wollastonprism 112 is parallel to X-Z plane and the C-axis of the second wedge ofthe second Wollaston prism 112 is perpendicular to X-Z plane. Uponexiting the second Wollaston prism 112, the light beams are recombinedinto a single light beam, which is focused into a TEC fiber of thesecond output port array 113.

A light beam input at the second port array 113 follows an optical paththrough the optical circulator array 100 to be output by an opticalfiber at the third port array 117. A light beam input at the second portarray 113 passes through the second Wollaston prism 112, which causesthe light beam to diverge into two orthogonally polarized light beams.After the TEC fiber the Gaussian beam divergence angle is reduced, whichallows two orthogonally polarized light beams to be clearly separatedangularly by Wollaston prism 112. The light beams pass through thesecond propagation direction dependent polarization rotation assembly inthe opposite direction to the propagation path from the first port array101 to the second port array 113. As a result, the second 45 degreeFaraday rotator 111 and a second 22.5 degree cut half wave plate 110provide a 90 degree polarization rotation in combination. However, bothlight beams remain orthogonally polarized with respect to each other.

Upon passing through the lens 109 a first orthogonal beam polarizedparallel to the X-Z plane passes directly to the birefringence wedgepair 107 while the second orthogonal beam passes through the 45 degreecut half wave plate 108 resulting in a polarization rotation of 90degrees before passing through the birefringence wedge pair 107. Thus,upon entering the birefringence wedge pair 107, both light beams havethe same polarization direction, which is parallel to the X-Z plane. Asa result, the birefringence wedge pair or port beam routing WollastonPrism 107 directs the light beams along a beam path toward the thirdport array 117.

The lens 105 focuses the light beams to a third propagation directiondependent polarization rotation assembly. The third propagationdirection dependent polarization rotation assembly includes a third 22.5degree cut half wave plate 114 and a third 45 degree Faraday rotator115. In the propagation direction from the second port array 113 to thethird port array 117, the third 22.5 degree cut half wave plate 114 andthe third 45 degree Faraday rotator 115 provide a 90 degree polarizationrotation in combination to each respective light beam.

The light beams exiting the third propagation direction dependentpolarization rotation assembly then enter a third Wollaston prism 116.Upon exiting the third Wollaston prism 116, the light beams arerecombined into a single light beam, which is focused into a particularTEC fiber of the third output port array 117.

Thus, the light beams are routed onto the path to the third port array117 after the Y-Z birefringence wedge pair 107. The arrangements ofpolarization rotation components including half wave plate 108, halfwave plate 106, half wave plate 114 and half wave plate 115 areconfigured that two beam components separated by the second Wollastonprism 112 when input from the second port array 113 can be recombined inthe third Wollaston prism 116.

Leakage of light in a reverse path of the circulator array 100 from thesecond port array 113 to the first port array 101 can be furtherisolated by the combination of the first 45 degree Faraday rotator 103and the first 22.5 degree cut half wave plate 104. In the lightpropagation direction of from the second port array 113 to the firstport array 101, the combination of the first 45 degree Faraday rotator103 and the first 22.5 degree cut half wave plate 104 will provide 90degree polarization rotation such that the leakage light, which has apolarization perpendicular to X-Z plane, cannot be recombined by thefirst Wollaston prism 102 and thereby cannot be directed to an opticalfiber of the first port array 101. Light leakage from the third portarray 117 to the second port array 113 can be similarly isolated.

FIG. 1C illustrates an array of three port optical circulators on theX-Z plane. In particular, the components described above, particularlythe layout of the input TEC fibers, first lens 105, birefringence wedgepair 107, second lens 109, and output TEC fibers are arranged in adouble telemetric configuration layout.

In a double telemetric configuration layout, the one or more TEC fibersof the first port array 101 and the third port array 117 are located ata rear focal plane of the first lens 105. The birefringence wedge pair107 for port beam path routing is located at the front focal plane ofthe first lens 105 and at the rear focal plane of the second lens 109.Similarly, the one or more TEC fibers of the second port array 113 arelocated at a front focal plane of the second lens 109.

Because of the optical features provided by the double telemetricconfiguration: the input beams from the TEC fibers at the first portarray 101 TEC fibers can be collimated by the first lens 105; the lightbeams crossing at the birefringence wedge pair 107 can also be refocusedby the second lens 109 to the TEC fibers of the second port array 113with a same incident angle; and the light beams input from a top TECfiber of the first port array 101 is imaged onto a bottom output TECfiber of the second port array 113. Similarly, the input beams from theTEC fibers of the second port array 113 can be collimated by the secondlens 109; the light beams crossing at the birefringence wedge pair 107can also be refocused by the first lens 105 onto the TEC fibers of thethird port array 117 with a same incident angle; and the light beamsinput from a top TEC fiber of the second port array 113 is imaged onto abottom output TEC fiber of the third port array 117. For each of theoutput ports, all the receiving TEC fibers are at the same focusingplane of the lens and the incoming light beams are of the same incidenceangle, so all the circulators in the array can be alignedsimultaneously.

FIGS. 2A-C illustrate an example optical circulator array 200 FIG. 2A isa diagram of the example optical circulator array 200 on a port beamrouting Y-Z plane. FIG. 2B is a diagram of an example single opticalcirculator of the optical circulator array 200 of FIG. 2A on apolarization conditioning X-Z plane. FIG. 2C is a diagram of the exampleoptical circulator array 200 of FIG. 2A on an array stacking andpolarization conditioning X-Z plane which illustrates light paths formultiple circulators of the optical circulator array 200.

The optical circulator array 200 includes a first port array 201, asecond port array 213, and a third port array 217. The opticalcirculator array 200 is configured such that an input beam from anoptical fiber at the first port array 201 is routed to an output opticalfiber at the second port array 213 and that an input beam from anoptical fiber at the second port array 213 is routed to an outputoptical fiber at the third port array 217. The optical circulator array200 provides an array of multiple three port optical circulators stackedon the X-Z plane. Each optical circulator of the array shares theoptical ports and optical components. The optical circulators of thearray can be aligned at the same time.

The optical circulator array 200 has a similar structure to the opticalcirculator array 100 of FIGS. 1A-C. In particular, the opticalcirculator array 200 includes optical components in a similarconfiguration including one or more TEC fibers at each port array, andfrom a propagation direction from the first input port array 201, afirst Wollaston prism 202, a first propagation direction dependentpolarization rotation assembly that includes a first 45 degree Faradayrotator 203 and a first 22.5 degree cut half wave plate 204, a firstlens 205, a 45 degree cut half wave plate 206, a birefringence wedgepair 207, a 45 degree cut half wave plate 208, a second lens 209, asecond propagation direction dependent polarization rotation assemblythat includes a second 45 degree Faraday rotator 211 and a second 22.5degree cut half wave plate 210, and a second Wollaston prism 212. Lightexiting the second Wollaston prism 212 passes through the second portarray 213.

In the direction of propagation of light beams from the second portarray 113 to the third port array 117, following the first lens 205, thecirculator array 200 includes a third propagation direction dependentpolarization rotation assembly and a third Wollaston prism 216. Thethird propagation direction dependent polarization rotation assemblyincludes a third 22.5 degree cut half wave plate 214 and a third 45degree Faraday rotator 215. Light exiting the third Wollaston prism 216passes through the third port array 217.

Light beams input at the first port array 202 follow beam paths to thesecond port array 213 through the above components in a similar manneras described above with respect to FIGS. 1 A-C. Similarly, light beamsinput at the second port array 213 follow beam paths to the third portarray 217 in a similar manner as described above with respect to FIG. 1A-C.

The optical circulator array 200 differs from the structure of theoptical circulator array 100 in the addition of optical X-Z plane wedgecomponents 218 and 219. The optical X-Z plane wedge component 218 ispositioned on a first side of the birefringence wedge pair 207 facingthe first lens 205. The optical X-Z plane wedge component 219 ispositioned on a second side of the birefringence wedge pair 207 facingthe second lens 209. The purpose of adding the optical X-Z plane wedgecomponents 218 and 219 is to correct beam parallelisms. In particular,because of the physical size and arrangement of the components in thecirculator array 200, the polarization beam separation optics, e.g.,first Wollaston prism 202, second Wollaston prism 212, and thirdWollaston prism 216, cannot be exactly located at the focal planes ofthe first lens 205 or the second lens 209. On the X-Z plane as shown inFIGS. 2B and 2C, the separated polarized beams cannot be collimated totwo exactly parallel beams after the collimating lenses 205/209 withoutthe additional correction provided by the wedge components 218 and 219.

FIG. 3A is a diagram of an example circulator array 300 on a port beamrouting Y-Z plane. FIG. 3B is a diagram of the example circulator array300 of FIG. 3A on an array stacking X-Z plane.

The optical circulator array 300 includes a first and third port arrayand a second port array. In particular, the first and third port arrayincludes TEC fibers and a micro-lens array 301. The second port arrayincludes TEC fibers and a micro lens array 310. The optical circulatorarray 300 is configured such that an input beam from an optical fiber atthe first port array is routed to an output optical fiber at the secondport array and that an input beam from an optical fiber at the secondport array is routed to an output optical fiber at the third port array.

Referring to FIG. 3A, a light beam input at the first port of the firstand third port array through a corresponding TEC fiber has a randompolarization. The input beam is collimated by a lens of the micro lensarray 301 and directed through a first Y-Z plane walk-off crystal 302.The first walk-off crystal 302 separates the incoming light beam intotwo beams having orthogonal polarizations. One of the two orthogonallypolarized light beams, which is initially polarized parallel to X-Zplane will pass through a first 45 degree cut half wave plate 303 andits polarization will be rotated by 90 degrees to the direction that isperpendicular to X-Z plane. The light beam will then pass through apropagation direction dependent polarization rotator component, a firstFaraday rotator 304. For light beams propagating in the direction fromthe first port array to the second port array, the propagation directiondependent polarization rotation assembly 304 provides 45 degreepolarization rotation.

The other polarized light component, which is initially polarizedperpendicular to X-Z plane, will be directly passed to the first Faradayrotator 304.

After the first Faraday rotator 304, the polarization direction of bothlight beams will be rotated by 45 degrees. However, due to the rotationby the first half wave plate 303 of one of the light beams, both lightbeams will share the same polarization orientation when they reach afirst Y-Z plane birefringence wedge pair 305, which may be a Wollastonprism.

The first birefringence wedge pair 305 includes two crystal wedgeshaving orthogonal crystal axes to each other. A C-axis of a first wedgeof the birefringence wedge pair 305 is at a 45 degree angle with respectto the X-Z plane and the Y-Z plane. The C-axis of a second wedge of thefirst birefringence wedge pair 305 is at a −45 degree angle with respectto X-Z plane and Y-Z plane. The first birefringence wedge pair 305 isused to separate the beam paths for from the first port to the secondport array 310 and from the second port array 310 to the third port.

Additionally, a second birefringence wedge pair 306 positioned followingthe first birefringence wedge pair 305 in the propagation direction fromthe first port to the second port array 310. The second birefringencewedge pair 306 is used to correct the parallelism of the beam paths.

Upon exiting the first birefringence wedge pair 305 and the secondbirefringence wedge pair 306, the two light beams are parallel to theZ-axis and are passed to a second Faraday rotator 307.

The second Faraday rotator 307 rotates the polarization of both lightbeams by 45 degrees such that the polarization direction of both lightbeams is parallel to the Y-Z plane. The light beam that was sent to thefirst birefringence wedge pair 305 from the first port without passingthrough the first half wave plate 303 passes through a second 45 degreecut half wave plate 308 and its polarization will rotated by 90 degreesto the direction that perpendicular to Y-Z plane. The two light beamsthen pass through a second walk-off crystal 309 where they are combinedinto a single light beam that is coupled to a lens 310 which focuses thelight beam on an output TEC fiber of the second port array.

In the propagation direction from the second port array to the thirdport array, a light beam is input from a TEC fiber of the second portarray and is collimated by a lens of micro lens array 310. The lightbeam is then separated into two orthogonally polarized beams by thesecond walk-off crystal 309. The light beam that is perpendicular to Y-Zplane is rotated 90 degrees by the second 45 degree cut half wave plate308 and is sent to the second Faraday rotator 307. The light beam with apolarization direction that is parallel to Y-Z plane is sent directly tothe second Faraday rotator 307.

The Faraday rotator is non-reciprocal and following the second Faradayrotator 307 the two light beams will have a polarization direction thatis orthogonal to the polarization direction of the light beam at thispoint of the optical circulator array 300 in the opposite propagationdirection from the first port array to the second port array. As aresult, the first and second birefringence wedge pairs 305 and 306 willdirect the light beams along a beam path toward the third port array.The two light beams are then directed through the first Faraday rotator304 and their polarization direction are rotated 45 degrees. A firstlight beam is rotated by 90 degrees by the first 45 degree cut half waveplate 303 and is then combined with the other light beam in the firstwalk-off crystal 302. The combined light beam exiting the first walk-offcrystal 302 is focused by a lens of the micro lens array 301 to aparticular TEC fiber at the third port array.

FIG. 3B shows an array of three port optical circulators stacked on theX-Z plane. The first port and the third port are a dual rowconfiguration on the Y-Z plane. The first dual row TEC fiber array islocated at the front of a first dual row lens array 301. The second portis a single row configuration on Y-Z plane and the second single row TECfiber array is located at a rear of the second single row lens array310. The different optical circulator arrays each share the samepolarization rotation assembly described above.

In particular, as shown in FIG. 3A, all optical pasts are in the Y-Zplane for each three port circulator. As shown in FIG. 3B, each of thelight beams from the first port array of TEC fibers are guided to theTEC fibers of the second port array and the light beams from the secondport array of TEC fibers will be guided to the TEC fibers of the thirdport array. The plane includes an optical path from a first port to asecond port and an optical path from the second port to a third port fora given three port circulator. Each plane is parallel to other opticalpath planes of other three port circulator of the array.

While this specification contains many specific implementation details,these should not be construed as limitations on the scope of anyinventions or of what may be claimed, but rather as descriptions offeatures specific to particular embodiments of particular inventions.Certain features that are described in this specification in the contextof separate embodiments can also be implemented in combination in asingle embodiment. Conversely, various features that are described inthe context of a single embodiment can also be implemented in multipleembodiments separately or in any suitable subcombination. Moreover,although features may be described above as acting in certaincombinations and even initially claimed as such, one or more featuresfrom a claimed combination can in some cases be excised from thecombination, and the claimed combination may be directed to asubcombination or variation of a subcombination.

Similarly, while operations are depicted in the drawings in a particularorder, this should not be understood as requiring that such operationsbe performed in the particular order shown or in sequential order, orthat all illustrated operations be performed, to achieve desirableresults. In certain circumstances, multitasking and parallel processingmay be advantageous. Moreover, the separation of various systemcomponents in the embodiments described above should not be understoodas requiring such separation in all embodiments, and it should beunderstood that the described program components and systems cangenerally be integrated together in a single software product orpackaged into multiple software products.

Thus, particular embodiments of the subject matter have been described.Other embodiments are within the scope of the following claims. In somecases, the actions recited in the claims can be performed in a differentorder and still achieve desirable results. In addition, the processesdepicted in the accompanying figures do not necessarily require theparticular order shown, or sequential order, to achieve desirableresults. In certain implementations, multitasking and parallelprocessing may be advantageous.

What is claimed is:
 1. An optical circulator array comprising: aplurality of stacked three port circulators each having a respectivefirst port of a first port array, a respective second port of a secondport array, and a respective third port of a third port array, whereineach of the plurality of staked three port circulators share opticalcomponents including: a first Wollaston prism coupled to the first portarray, a first lens, a first half wave plate, a polarization dependentbeam path separator, a second half wave plate, a second lens, apropagation direction dependent polarization rotation assembly, a secondWollaston prism coupled to the second port array, and a third Wollastonprism coupled to the third port array.
 2. The optical circulator arrayof claim 1, wherein the propagation direction dependent polarizationrotation assembly includes a Faraday rotator and a half wave plate. 3.The optical circulator array of claim 1, wherein each port arrayincludes one or more thermal expansion core (TEC) fibers.
 4. The opticalcirculator array of claim 1, wherein the polarization dependent beampath separator comprises a birefringence wedge pair.
 5. The opticalcirculator array of claim 4, wherein the birefringence wedge paircomprises: a first wedge optically coupled to a first side of thebirefringence wedge pair; and a second wedge optically coupled to asecond side of the birefringence wedge pair, wherein the first wedge andthe second wedge correct parallelization of light beams passing throughthe optical circulator array.
 6. The optical circulator array of claim1, wherein the polarization dependent beam path separator comprises anoptical beam separator with polarization dependent coating.
 7. Theoptical circulator array of claim 1, wherein the TEC fibers, first lens,second lens, and polarization dependent beam path separator arepositioned in a double telemetric configuration layout.
 8. The opticalcirculator array of claim 1, wherein the polarization dependent beampath separator provides beam path routing from the first port to thesecond port and from the second port to the third port based on apolarization orientation of incident light beams.
 9. The opticalcirculator array of claim 1, wherein the polarization dependent beampath separator is optically coupled between the first lens and thesecond lens.
 10. The optical circulator array of claim 1, wherein thepropagation direction dependent polarization rotation assembly isoptically coupled between the second Wollaston prism and the secondlens.
 11. The optical circulator array of claim 1, further comprising: asecond propagation direction dependent polarization rotation assemblycoupled to the first port; and a third propagation direction dependentpolarization rotation assembly coupled to the third port, wherein thesecond propagation direction dependent polarization rotation assembly isoptically coupled between the first Wollaston prism and the first lens,and the third propagation direction dependent polarization rotationassembly is optically coupled between the third Wollaston prism and thefirst lens.
 12. The optical circulator array of claim 1, wherein thesecond propagation direction dependent polarization rotation assemblyprovides isolation to reduce light leakage along a path from the secondport to the first port.
 13. The optical circulator array of claim 1,wherein the third propagation direction dependent polarization rotationassembly provides isolation to reduce light leakage along a path fromthe third port to the second port.
 14. The optical circulator of claim1, wherein light beams input at the first port are randomly polarizedand wherein the first Wollaston prism and the first half wave plateprovide polarization conditioning.
 15. An optical circulator arraycomprising: a plurality of stacked three port circulators each having arespective first port of a first port array, a respective second port ofa second port array, and a respective third port of a third port array,wherein each of the plurality of staked three port circulators shareoptical components including: a first micro lens array optically coupledto the first port array and the third port array, a first walk offcrystal, a first half wave plate, a first faraday rotator, a firstbirefringence wedge pair, a second birefringence wedge pair, a secondFaraday rotator, a second half wave plate, a second birefringence walkoff crystal, and a second micro lens array optically coupled to thesecond port array.